Characteristics of single particles sampled in Japan during the Asian dust-storm period

To investigate the characteristics of Asian dust storm particles as single particles in Japan, we measured morphology, composition and concentration o f single particles using Scanning Electron Microscope (SEM) coupled with an energy dispersive X-ray microanalyzer (EDX), particle induced X-ray emissi on (PIXE) and micro-PIXE. Particles were sampled in Kyoto, Japan from the m iddle of April to the end of July 1999. Mass concentration in Asian dust-st orm events was roughly 3-5 times higher than that of the highest concentrat ion measured in non-Asian dust storm seasons. Single particles were general ly sharp-edged and irregular in shape and contained mostly crustal elements such as Si, Fe, Ca and Al. Particles which have more than 40% Si content c omprised nearly 50% of coarse single particles in Asian dust storm events. Main concentration range of Al in single Asian dust storm particles was 10- 20%, and those of Ca and Fe were below 10%. Even though S and Cl in soils o f the desert and loess areas in northwest of China were not detected, signi ficant concentration of S and Cl in coarse fraction in Asian dust storm eve nt were detected in single particles. Especially, the maximum concentration of S in Asian dust storm event was about 5 times higher than that in non-A sian dust storm days. Every single particle in coarse fraction existed as t he mixing state of soil components and S. Good agreement between the result s of SEM-EDX analysis and that of micro-PIXE analysis was obtained in this study. (C) 2001 Elsevier Science Ltd. All rights reserved.